Diabetes mellitus is the fastest growing diagnostic class in the cardiovascular and end stage renal disease population, accounting for almost half of all patients beginning dialysis. It is therefore a major health care problem. However the basic underlying mechanisms are not very clear. Emerging evidence strongly supports a role for free fatty acids and oxidized lipids in complications such as diabetic nephropathy (DN). Examining the mechanisms involved can provide critical information regarding the pathophysiology of complications associated with Type 1andType 2 diabetes. In the previous fundingperiod, weidentified key mechanisms InitiatedbyAngiotensin II (AngII) and high glucose Inrenalmesangial cells (MC) andalso accumulated extensive evidence that these diabetic stimuliregulate the formation of oxidizedlipids of the 12/15-lipoxygenase (LO)pathway of arachldonate metabolism both In vitro and in vivo. These lipids induced cellular hypertrophy, profibrotic and extracellular matrix genes in mesangial cells by regulating specific signaling pathways and transcription factors. We demonstrated in vitro and in vivo relevance to diabetes, DN, proteinuria and vascular dysfunction and made significant progress in understanding the signal transduction events involved. In this renewal, we will extend our studies based on new observations of novel cross-talk mechanisms by which the LO pathway interacts with growthfactor signaling pathways to augment fibrotic gene expression. We will use novel gain- and loss-of-function approaches to examine how LO lipid products and diabetogenic agents mediate the pathogenesis of DN 1) by inducing the expression of fibrotic genes via novel nuclear transcriptomic events in MC; 2) by orchestrating key oxidative and survival events in MCs; 3) by playing key roles in the progression of DN in mouse models of type 1andtype 2 diabetes. Ouroverall hypothesis is that: Diabetesand insulin resistance lead to increased activity andexpression of 12/15-LOin glomerular MCs and tills leads to key changes associatedwith both early andlate stages ofDN. This Is a consequenceof 12/15-LO mediation of growth factorandhigh glucose (HG)effects andaugmentedexpression of profibrotic and cellsurvivalrelated genes. Four Specific Aims will usestate-of-the-art approaches to test the cellular, molecular and signal transduction mechanisms of actions of LO products, as well as consequences of genetic overexpression, and knockdown with LO knockout mice or siRNA treated cells and mice. These integrated in vitro and in vivo studies are expected to provide new information on the pathologyof glomerular disease in diabetes and also lead to the identification of novel new therapeutic targets.